The Somua S40 was a prototype French tank developed before the Second World War.

Compared with the latter, the S40 had a new 220 hp (160 kW) diesel engine; its hull was longer than the S35; and an extra pair of wheels was added on the suspension.

Mass production was planned for the S40.

However, production was cancelled after the Fall of France in 1940.

This military vehicle article is a stub.